33 research outputs found
Crowding of Polymer Coils and Demixing in Nanoparticle-Polymer Mixtures
The Asakura-Oosawa-Vrij (AOV) model of colloid-polymer mixtures idealizes
nonadsorbing polymers as effective spheres that are fixed in size and
impenetrable to hard particles. Real polymer coils, however, are intrinsically
polydisperse in size (radius of gyration) and may be penetrated by smaller
particles. Crowding by nanoparticles can affect the size distribution of
polymer coils, thereby modifying effective depletion interactions and
thermodynamic stability. To analyse the influence of crowding on polymer
conformations and demixing phase behaviour, we adapt the AOV model to mixtures
of nanoparticles and ideal, penetrable polymer coils that can vary in size. We
perform Gibbs ensemble Monte Carlo simulations, including trial
nanoparticle-polymer overlaps and variations in radius of gyration. Results are
compared with predictions of free-volume theory. Simulation and theory
consistently predict that ideal polymers are compressed by nanoparticles and
that compressibility and penetrability stabilise nanoparticle-polymer mixtures.Comment: 18 pages, 4 figure
Inflammatory bowel disease in children and adolescents in Italy: data from the pediatric national IBD register (1996-2003).
Inflammatory bowel disease in children and adolescents in Italy: data from the pediatric national IBD register (1996-2003).
Abstract
BACKGROUND:
The purpose was to assess in Italy the clinical features at diagnosis of inflammatory bowel disease (IBD) in children.
METHODS:
In 1996 an IBD register of disease onset was established on a national scale.
RESULTS:
Up to the end of 2003, 1576 cases of pediatric IBD were recorded: 810 (52%) ulcerative colitis (UC), 635 (40%) Crohn's disease (CD), and 131 (8%) indeterminate colitis (IC). In the period 1996-2003 an increase of IBD incidence from 0.89 to 1.39/10(5) inhabitants aged <18 years was observed. IBD was more frequent among children aged between 6 and 12 years (57%) but 20% of patients had onset of the disease under 6 years of age; 28 patients were <1 year of age. Overall, 11% had 1 or more family members with IBD. The mean interval between onset of symptoms and diagnosis was higher in CD (10.1 months) and IC (9 months) versus UC (5.8 months). Extended colitis was the most frequent form in UC and ileocolic involvement the most frequent in CD. Upper intestinal tract involvement was present in 11% of CD patients. IC locations were similar to those of UC. Bloody diarrhea and abdominal pain were the most frequent symptoms in UC and IC, and abdominal pain and diarrhea in CD. Extraintestinal symptoms were more frequent in CD than in UC.
CONCLUSIONS:
The IBD incidence in children and adolescents in Italy shows an increasing trend for all 3 pathologies. UC diagnoses exceeded CD